1. Field of the Invention
The invention relates to a self-propelled road milling machine for working road surfaces and a method for working road surfaces.
2. Description of the Prior Art
Such road milling machines are already generally known. For small milling machines, in which the milling drum is located level with the rear axle of the chassis and between the rear wheels, it is known to provide a rear support wheel or tracked ground-engaging unit on the zero side of the machine which can pivot inwards behind the outer contour of the road milling machine for close-to-edge milling.
Large milling machines are road milling machines, for example, in which the milling drum is mounted at the machine frame between the tracked ground-engaging units of the front axle and the rear axle, and at a distance to the same. EP 1 167 626 A1 (U.S. Pat. No. 7,644,994) describes such a large milling machine.
The milling drums of such milling machines comprise multiple tools circumferentially preferably arranged in the shape of a helix. These are usually milling tools which are fixed in place in toolholders welded onto a cylindrically hollow drum body or in toolholder systems. The tools therefore exhibit a constant line spacing which corresponds to the axial distance between neighbouring tools and, as a rule, ranges between 3 mm and 25 mm.
Due to the axial distance of the tools, a grooved texture is created on the milled surface during the milling process, wherein the mutual distance of neighbouring grooves corresponds to the line spacing.
In the process, the selection of the line spacing depends on the particular milling application. For the removal of complete pavements, for example, a larger line spacing is usually selected than for fine milling which merely serves to roughen the pavement surface at a small milling depth.
In simple terms, the reason for this is that milling drums with a small line spacing are not suitable for large milling depths due to the high tool density, whereas milling drums with a large line spacing do not achieve the desired texture for roughening the pavement as the grooved texture produced in the milled surface is too coarse.
Furthermore, in addition to the milling depth and desired surface texture, a multitude of other factors play a role in the selection of the line spacing, such as the nature of the ground to be worked, which leads to a multitude of different milling drums with different line spacings being available for different applications.
For milling contractors, this results in the necessity to maintain different milling machines and/or different types of milling drums for a milling machine for different applications.
This results in additional costs for the acquisition of additional machines, or an additional amount of work and expenditure of time, respectively, for conversion of the machines with different milling drums. This is of disadvantage in particular in those cases where different requirements need to be met on a single construction site and, as a result, different machines need to be transported to the operating site or a single machine needs to be converted on site.